The present invention relates to installations for the continuous manufacture of slabs obtained by molding a settable molding material. More particularly, it is concerned with an apparatus for filling the molds in such installations.
French printed patent application No. 2,144,520 discloses an installation for the continuous manufacture of slabs by molding a settable molding material, such as a concrete mix. The installation comprises a conveyor belt equipped with molds made of flexible material, the conveyor being adapted to advance the molds at right angles to a distributing station designed to meter the material accurately, the molds being advanced automatically without being subjected to harmful pressures.
With this in view the above identified French patent publication disclosed a distributing station comprising a loading hopper and a vibrating consolidating table, the loading hopper being associated with a vibrator adapted to impart essentially vertical vibrations thereto, whereas essentially horizontal vibrations are imparted to the table. The loading hopper is advantageously mounted on the vibrating table with a resilient suspension. The hopper is further provided, at its lower end, with an extension surrounding its discharge aperture; the extension has a flat lower surface parallel to the plane in which the molds are displaced, so that it covers an area larger than each of the molds. The lower surface is designed to cooperate with the top edge of each mold, so as to form a tight seal with the top edge.
The distributing station comprises a structure in which the loading is adapted to fill the molds with a metered quantity of molding material by direct contact with the upper edges thereof, and to keep the concrete mix in a suitable visco-plastic state, while the vibrating table imparts shearing forces to the molds, to assist discharge of the molding material from the hopper.
Now, it has been found in practice that an arrangement of this type does have disadvantages.
First, it has been found that complex means, chiefly in connection with the mounting of the hopper, are required. This is mainly due to the fact that the loading hopper has to vibrate vertically while at the same time forming a seal between its lower end and the edges of the mold.
Secondly, maintenance costs have been found to be considerable, and relatively frequent stoppages of the installation are required, with the consequent unreliable production rate affecting the cost of the finished product.
Finally, it has been found that the distribution of the molding material within the molds has not been uniform and has caused defects, so that molds which were not completely filled produced unusable slabs.